Module: command_meta.IF

Overview

Module

This module provides a simple /IF command.

It can be used to express conditional logic, such as IF ... THEN ... ELSE ....

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Note

◉ How it works?

The syntax of /IF command is: /IF <condition-command> THEN <then-command> ELSE <else-command>

The IF, THEN, ELSE literals must be capitalized.

The execution flow of this command is as follows:

Start the execution of a given /IF command instance.
Check the possible ambiguity of the given /IF command instance.

2.a. If no ambiguity found, goto step 3.

2.b. If there is an ambiguity found, abort the entire execution of /IF command.

Execute the condition-command, and get its return value:

3.a. If the return value is true, then executes the then-command.

3.b. If the return value is false, then executes the else-command.

◉ Any failure will lead to the execution of else-command.

If there is any error during the execution of condition-command, the else-command will be executed.

For example, the /IF bad command THEN say true ELSE say false command will do the following things:

First, execute the /bad command.
Due to the error during the execution of /bad command, the /say false command will be executed.

◉ Recursive IF is not supported.

The /IF command is a simple enough command, to provide a very basic conditional expression.

The nested IF is not supported.

Once there is an ambiguity found in the /IF command, the entire execution of the /IF command will be aborted.

Note

◉ The difference between /IF command and /execute if command.

The /execute if command is a powerful command:

You can use recursive if.

For example: /execute if <first-condition> if <second-condition>

You can use lots of built-in Minecraft predicates.

For example: /execute if {block|biome|loaded|dimension|score|blocks|entity|predicate|function|items|data}

You can simulate the else-clause by combining the /execute if and /execute unless commands.

◉ What is the purpose of /IF command?

It allows you to use any command as the condition, based on the return value of that command.
It prevents the side-effect from the condition-clause and then-command. (Without the /tag or /scoreboard)
It provides a simple and in-line way to express the IF ... THEN ... ELSE ... logic.
It supports the placeholders.
Still, You can leverage the /execute if command as the condition-command of /IF command.

Note

◉ Use /command-debug command to see the return value of a command.

The return value is not displayed explicitly in-game.

However, you can use /command-debug command to see the return value of a specified command.

Issue:

/command-debug execute if block ~ ~-1 ~ minecraft:diamond_block
/command-debug execute if block ~ ~-1 ~ minecraft:diamond_block if entity @s[nbt={Inventory:[{id:"minecraft:diamond"}]}]

◉ The behaviour of /execute if command.

When none condition is true, it throws a Test failed exception.
When one of the specified conditions is true, it will returns 0 to mean partial success.
When all of the specified conditions are true, it will returns a positive integer to mean success.

NOTE: This positive integer equals to the number of successful branch if the /execute if command is forked.

For example, if you have 3 players online, but only 2 of them are standing on a minecraft:diamond_block block.

Issue: /command-debug execute at @a if block ~ ~-1 ~ minecraft:diamond_block

You will get the integer 2 as the return value of that /execute ... command instance.

Tip

◉ Useful commands.

Tip

◉ Write the IF ... THEN ... ELSE ... logic conveniently.

You can use command_bundle module to create a template command to help you write conditional logic.

For example, you can create a new command /try-give-item <item> <required-balance>.

Example

◉ Check whether a player is an operator.

Issue: /IF is-op? %player:name% THEN say It is op. ELSE say It is not op.

◉ Check whether a player has sufficient balance.

Issue: /IF has-currency? %player:name% fuji:gold 100 THEN say Sufficient balance. ELSE say Insufficient balance.

◉ Use a shorten version of /IF ... THEN ... command.

The /nop command performs no action and always returns success.

You can use it as a dummy command in the else-command place, to effectively ignore it.

Issue: /IF is-op? %player:name% THEN say It is op. ELSE nop

◉ Specify multiple commands in one place, by using the /chain command.

Issue: /IF is-op? %player:name% THEN chain say It is op. chain say Hello op! ELSE nop

◉ Leverage the power of /execute if. (And the /execute unless command)

Issue: /IF execute if block ~ ~-1 ~ minecraft:diamond_block THEN say You are standing on diamond block. ELSE say You are not standing on diamond block.

◉ Combine 2 conditions using chained if, and only execute the then-command when they are all true.

Issue: /IF execute if block ~ ~-1 ~ minecraft:diamond_block if entity @s[nbt={Inventory:[{id:"minecraft:diamond"}]}] THEN say All true. ELSE say Not all true.

The then-command will only be executed if the condition-command is true:

The player is standing on a minecraft:diamond_block block.
The player has a minecraft:diamond item in its inventory.

Example

◉ Filter all the online players by a predicate

You can integrate /IF with the /foreach command.

/foreach IF <predicate-command> THEN ... ELSE ...
/foreach IF has-item? %player:name% minecraft:apple 1 THEN say Player %player:name% has an apple. ELSE nop
/foreach IF is-in-world? %player:name% minecraft:overworld THEN say Player %player:name% is in overworld. ELSE nop

◉ Leverage the vanilla Minecraft's /tag command, to store states.

Example:

/tag Steve add killed_the_dragon
/execute if entity @a[tag=killed_the_dragon]

◉ Leverage the vanilla Minecraft's /scoreboard command, to store states.

It's similar to /tag command, but more advanced.

Commands

Command

Command Syntax: /IF <GreedyString rest>
Document: null
Can be executed by console: true
Required Level Permission: 4
Required String Permission: null

Overview​

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Commands​

Overview

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Commands